When it comes to fluorescent lights, it is pretty much impossible to have too much light because they emit so few lumens. Just so you know what I mean, my MH light puts out 75,000 lumens and my HPS puts out 95,000.
Get those lights as close as you can without getting the plant too hot. If you have a thermometer(which you should get if you do not have one), measure the temperature at the plant in between the plant and the light. You want about 80 degrees(some strains like higher, some lower so if you know what strain you have, you can look it up). Measure the temp after the lights have been on for a few hours. If the temp is lower than that then you can bring your lights closer. Fluros don't emit a lot of heat so chances are you might be able to bring those lights closer but don't do it without checking temps first. The closer you can get them without making the plant too hot, the better.
You will also want to start using a fan, preferably oscillating. Do not blast it on the plant but you definitely want the plant to get a nice breeze. This will help build a better root system and stronger stems. It will also help remove stale air from around the leaves and replace it with fresh air.